165 



result of a downthrow on the south-east side, or on the right hand 

 side of the letter, if the upper limb be regarded as representing the 

 north of the map. 



For the correct understanding of what is to follow, it will be 

 necessary to obtain a general idea of the lie of the rocks that occur 

 on each side of the zone of disturbances now referred to. The 

 phenomena are complicated, and somewhat difficult to explain to 

 the non -geological reader ; but some insight into the nature of the 

 changes that take place may be gathered by means of one or two 

 simple experiments, if the reader have the faculty of mentally 

 extending an idea formed in the first instance from an examination 

 of objects on a small scale to the phenomena in the field on a 

 scale large enough to extend over a line twenty or twenty-five 

 miles in length. 



All, or nearly all, except the volcanic strata of our district, were 

 originally deposited in beds that were nearly or quite horizontal ; 

 so that their normal position, where they are undisturbed, is that 

 of great piles of sheets of sandstone, shale, limestone, and so on, 

 piled one over another up to an aggregate thickness, that ranges 

 from a few hundred feet to as many thousands, and may, in the 

 case of one or two groups, really be stated in miles. Now a 

 moment's reflection will convince any one that, if these strata all 

 lay in the horizontal position natural to them when they were first 

 formed, we should have very little opportunity of learning anything 

 of the nature of the strata that lay near the bottom, unless we had 

 valleys deep enough to cut through the pile from the top to the very 

 bottom, and that would mean that we should have either valleys 

 six or seven miles in depth (as the total thickness of the existing 

 strata of Cumberland and Westmorland is not far short of that) or 

 else, putting the same statement in another form, we should have 

 mountains towering to an elevation of as many miles above the 

 level of the lowest part of the surface. As a matter of fact we 

 know that this is not the case, and the exposure of the great thick- 

 nesses of rock that are now out to the day in one part or another 

 of the district have, clearly, resulted from the action of subsequent 

 causes that have affected the lie of the strata, and disturbed them 



